Dale Amy
June 2, 2010

With crude oil being a finite and mostly imported resource, the search is well and truly on these days for alternative fuels to serve our energy needs. While some take an environmentally zealous, politically pious, or unrealistically utopian view about the preferred types of alternatives to gasoline, the more levelheaded amongst us would surely rank availability, viability, and affordability at the top of the criteria list when considering any such alternatives.

Those three pragmatic criteria have made propane pretty popular not just for heating our homes and cooking our steaks, but also as a transportation fuel, where it ranks third behind only gasoline and diesel. That said, we've never before seen propane used to fuel a drag car, but that's about to change.

For the 2010 NMCA and NMRA season, Susan Roush McClenaghan's She-Devil Motorsports-part of the Roush Drag Team-is fielding a freshly constructed '10 Mustang powered by a naturally aspirated Four-Valve modular fueled by liquid propane.

Why propane? "I was trying to find a way," Susan explains, "to tie our drag racing into the other parts of the [Roush] business, and this project demonstrates a number of those pieces-our engine build services, our liquid propane technology, paint and body services... The other reason for looking at propane is I want to take our race program and really have it stand out in terms of current events, so to speak, with emphasis on alternative fuels and concern for being ecologically responsible."

In the foregoing quote, Susan is referring to Roush Industries' recent forays into the business of engineering and supplying liquid-propane fuel-injection systems for the conversion of fleet vehicles (currently various Ford pickup and van platforms). The research and development invested in that fleet conversion program were harnessed in building her new race car.

The use of propane-more formally, liquified propane gas, or LPG-as a motor fuel has been around for decades, but Roush's fleet and race programs harness the efficiencies and drivability of liquid propane injection systems (older-technology agricultural and fleet propane conversions were vapor-based systems saddled with vaporizers/mixers and carburetors). Check out our sidebar The Science of Propane for more on the fuel itself.

Our mid-winter visit to the Roush race shops coincided with the first trial merging of the project's development engine and chassis, the latter having started off as a '10 Mustang body-in-white, now constructed to NHRA Super Stock specs. By comparison, Susan's previous two New Edge drag 'Stangs were simply converted production cars, so this purpose-built racer is a serious step up. Expect to see it in the NMRA's Modular Muscle class and some NMCA events.

The complete development engine in our photos is based upon a stock-displacement Ford GT aluminum block and heads, and is essentially an R&D tool used to develop, package, and test the propane fuel system. This engine has been run on the Roush brake dynos in two forms: initially with a normal gasoline fuel system in place; then, otherwise unaltered aside from recalibration of its FAST XFI processor, with the new liquid-propane injection hardware onboard.

Showing the viability of propane as a gasoline substitute, the engine produced similar power figures when fed either fuel-between 625 and 635 hp. By the time you read this, a second engine will be in place-the real race engine. It will have a similar aluminum 5.4-liter basis, but will be bored and stroked to about 374 cubes, with a target horsepower in naturally aspirated form of somewhere around 700. If the program proves successful, supercharging may be added for next season.

Our captions contain much more detail, but overall, the only real challenges to adaptation of a liquid-propane injection system for race purposes were in the specifics of the fuel system itself. That's to say that the engine internals-crank, rods, piston, compression, cams, and so on-are no different than if the modular were built to run on gasoline. Of course, the Roush team also needed to develop an efficient means of fueling (and de-fueling) the car at the racetrack, and even for fueling the engine on the dyno stand, as our photos show.

Will we ever see widespread use of propane in the Ford drag racing scene? We would guess it unlikely at least in the near term, but racing, like hot-rodding, is all about experimentation, so who knows?

Horse Sense: Roush Industries reports that propane combustion produces roughly 20 percent less nitrogen oxides and 60 percent less carbon monoxide than gasoline combustion.